The use of devices for the separation of whole blood or into its constituent components is widespread. Such devices commonly utilize centrifuges (that separate the cellular components based on their density) or filter membranes (that separate the cellular components based upon their size).
Typically, the control of fluid into and out of a centrifugal or spinning membrane separation device has been accomplished by applying a first pump to the inlet line of the separator to supply a blood source, and a second pump applied to either a first outlet line (for the retentate, in the case of a spinning membrane separator) or a second outlet line (for the filtrate in the case of a spinning membrane separator) to control the flow of fluid through the membrane.
In the case of a spinning membrane separator, to force a fluid to flow across a membrane a gradient must be formed across the membrane. For a spinning membrane separator, a pressure gradient, commonly referred to as the transmembrane pressure (TMP), is generated to force fluid (filtrate) to flow through the membrane while particles or cells (retentate) greater than the membrane pore size are retained. See, e.g., US 2013/0345674, which is incorporated herein by reference. For example, if the inlet pump is pumping at 50 ml/min and the retentate pump in pumping at 30 ml/min, a TMP will be produced and filtrate will flow through the membrane at 20 ml/min (difference between inlet and retentate rates).
While the use of a pump on each of the inlet line and outlet line(s) of the separation system has proven to be effective for many applications, there is a desire to simplify the required hardware and to reduce the size of the system.